How to hang from ceiling when stud finder isn't working

Question

I want to hang a fluorescent strip light over my workbench in the garage. The problem is that I don't see how to determine where the joists are; the ceiling is some sort of weird 3-dimensional meringue that prevents me from using a stud finder. (This area is ~12 feet from the area I'm looking at, I used this picture so that the scale of the meringue could be derived against the power outlet)

Any suggestions as to how you would do it?

Some other pictures for context (click to see full size version):

And yes, the first thing someone will say is "Where does that power conduit go in the attic?" Here it is:

The answer is, in an area of the attic with flooring blocking access. And because that wasn't enough to make my life hard, the nice insulation people threw every piece of wood they found in the attic on top of the one area I'd like to have access to:

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For the record, I used a drill to probe for the joist. As it turns out, there's a gap between the ceiling and the joist, and the drill bit I used wasn't deep enough to hit the joist. As a result, I may have used more holes than was strictly necessary:

Fortunately, I went back with a long allen wrench and probed more deeply in each hole, and eventually found the joist behind one of them. Screwing in two hooks was trivial and my light is now hanging where I need it:

Answer 1

Assuming you really want to use a joist...

The outlet you show is probably mounted to a joist. Remove the cover and you should be able to see the joist on one side or another. Then measure over 16 inches (I'm assuming 16 on center joist spacing) to get an approximate location of the next joist (or 32 inches for the 2nd joist). Then drive a small finishing nail or use a small drill and see if you hit wood. If you don't then move the nail or drill over ~1 inch & try again.

A fluorescent light fixture is pretty light. You can probably hang that with a pair of toggle bolts, something like this (picture from Home Depot):

Answer 2

Ways to find a ceiling joist when an electronic stud finder won't. These are in order of increasing destructiveness.

1. Use a magnet to find nails. There are magnetic stud finders designed for ceilings, where a magnet is on a hinge and gets pulled up by a nail. Like a compass. These work pretty well, although they are sometimes a pain to use especially if there are stray nails or if the ceiling was built with furring strips or shims ... then you'll find those.
2. Buy a better stud finder. I have a cheap one I bought 20 years ago. It has two "modes". Sometimes one works, sometimes the other, sometimes neither works. I've seen some fancy ones advertised recently that are a lot more sensitive and will even differentiate wood, plastic, and metal even if it's not touching the plaster. I haven't bought one, but it's something to consider.
3. Buy a dual-camera borescope and drill one (or a few) 1/2 inch holes for access. Look inside the ceiling. These cameras are surprisingly cheap. I just bought one for $60 (2022) and it's great.
4. Drill small test holes in random places til you find some joists. You can feel when the drill hits a joist. Then drill them in decreasingly random places til you develop a pattern.
5. If you know which way the joists run, use a plaster saw to saw slits in the ceiling til you hit the joists.

In all these cases you run the risk of mistaking furring strips and shims for joists but none of this matters if all you are hanging is a lightweight light fixture. In fact, you don't need a joist at all for that.

Answer 3

That meringue stuff is a layer of plaster often called stippling, and is purely decorative. It is probably stuck to drywall. Do note that older plaster may have asbestos in it - in some areas of the world it was not illegal through into the 90s.

Since you're planning on putting fluorescent tube fittings there, you'll have a better time if the underside of the ceiling is flat. You also mention this is for a workbench over a garage, so its not a "nice" area of the home.

I would suggest clearing the floorspace, remove all the food, close all the internal doors, seal the locks and cracks with tape, cover yourself with overalls, goggles and mask (a respirator if you can) then pull the stippling off with whatever tool you have handy.

Warning: it's going to make an enormous dusty mess in the garage.

If you're lucky it will come off in chunks and drop down for sweeping. Otherwise you may need to pry at it with a long-handled garden hoe or any sort of paint scraper. Sanding may help, use 40 grit paper in a pole sander. Finally treat the exposed drywall with undercoat then plain ceiling paint in white.

It is a garage, doesn't need to be perfect quality finish. The plaster is hard to clean at any time, and is surprisingly heavy which can cause the ceiling to sag over time.

Yes, this is a torturous and long-winded way of allowing OP's stud finder to work better. It may be acceptable to simply clear the area where the workbench will be rather than the whole room.